Bifidobacteria are known as useful microorganisms in the intestine of animals inclusive of human beings, and their usefulness has been clinically proved, for example, for therapy or prevention of various symptoms or diseases such as diarrhea, constipation and infectious diseases, and for growth-inhibition against harmful intestinal microorganisms.
Various substances having growth-promoting activity to Bifidobacteria have been reported, for example, N-acetylglucosamine, pantethinic substances, various peptides and nucleic-acid-related substances as well as various saccharides (such as lactulose) which are not digested by gastric acid and which are utilized by Bifidobacteria.
The present invention provides new bioactive agents having growth-promoting activity to Bifidobacteria, which are completely different from those substances which had been known to have growth-promoting activity, and which consist of one or more lactoferrin-compounds selected from the group consisting of bovine lactoferrin, bovine apolactoferrin and bovine Fe-lactoferrin.
Meanwhile, lactoferrin is known as an iron-binding protein occurring, in vivo, in lacrima, saliva, peripheral blood and milk and the like. Lactoferrin content in cow's milk is 1/10 of that in human milk, and it has been known that bovine lactoferrin has antibacterial activity to harmful microorganism belonging to the genuses of Escherichia, Candida and Clostridium and the like [cf: Welsh, J. K. and J. T. May; Journal of Pediatrics; Vol. 94; Page 1; 1979].
It has been reported that bovine apolactoferrin, which is obtainable by unbinding iron from lactoferrin originating from cow's milk, may inhibit proliferation of harmful microorganisms belonging to the genuses of Escherichia, Staphylococcus and Enterococcus and the like in synthetic medium with a concentration of 0.5-30 mg of the apolactoferrin per ml medium [Nonnecke, B. J. and K. L. Smith; Journal of Dairy Science; Vol. 67; Page 606; 1984].
It has been considered in general that apolactoferrin may act to inhibit proliferation of microorganisms, which require iron strongly, due to chelation of iron with apolactoferrin.
On the other hand, it has been known that human Fe-lactoferrin, which is obtainable by saturating human lactoferrin with Fe, may enhance or promote proliferation of Bifidobacteria which are typical and useful microorganisms found in the human intestine [Kodama; Nihon Shohnika Gakukaizasshi (The Journal of Japanese Pediatrics Society); Vol. 87; Page 1000; 1983].